Thimerosal is used at the early stages of manufacture and is removed by subsequent purification steps to a trace amount (≤1 mcg mercury per dose). Each dose may also contain residual amounts of hydrocortisone ≤0.0016 mcg, gentamicin sulfate ≤0.15 mcg, ovalbumin ≤1 mcg, formaldehyde ≤50 mcg, and sodium deoxycholate ≤50 mcg from the manufacturing process.